1 #include <string> 2 3 using namespace std; 4 using std::string; 5 using x = std::string; 6 7 class A 8 { 9 public: 10 void test(); 11 }; 12 13 class B : public A 14 { 15 public: 16 void test(x t); 17 using A::test; 18 };